The study was terminated for strategic reasons.

To investigate the brain receptor occupancy of idalopirdine in patients with Alzheimer's disease (AD)

Inclusion Criteria:

• The patient has probable AD diagnosed according to National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's disease and Related Disorders Association (NINCDS-ADRDA) criteria.
• The patient has had a positive amyloid PET scan, which in the opinion of the principal investigator is consistent with a diagnosis of AD.
• The patient has a Mini Mental State Examination (MMSE) score at screening of at least 15 and no greater than 22.
• The patient has a knowledgeable and reliable caregiver who will accompany the patient to all clinic visits during the study and answer questions about the patient.
• The patient is a man or woman of at least 50 years of age and has a body mass index (BMI) ≥ 18.5 kg/m2.

Exclusion Criteria:

• The patient has evidence of any clinically significant neurodegenerative disease, or other serious neurological disorders other than AD including but not limited to Lewy body dementia, fronto-temporal dementia, Parkinson's disease, Huntington's disease, major cortical stroke, major head trauma, primary or secondary cerebral neoplasia or systemic medical diseases that are, in the investigator's opinion, likely to affect central nervous system functioning and may influence the outcome or analysis of the scan results.
• The patient is, in the investigator's opinion, unlikely to comply with the protocol or is unsuitable for any reason.